A type of endoprosthesis device, commonly referred to as a stent, may be placed or implanted within a vein, artery or other tubular body organ for treating occlusions, stenoses, or aneurysms of a vessel by reinforcing the wall of the vessel or by expanding the vessel. Stents have been used to treat dissections in blood vessel walls caused by balloon angioplasty of the coronary arteries as well as peripheral arteries and to improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Two randomized multicenter trials have recently shown a lower restenosis rate in stent treated coronary arteries compared with balloon angioplasty alone (Serruys, P W et al., New England Journal of Medicine, 331: 489-495 (1994) and Fischman, D L et al., New England Journal of Medicine, 331:496-501 (1994)). Stents have been successfully implanted in the urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others. The term “stent” as used in this Application is a device which is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.
One of the drawbacks of conventional stents is that they are generally produced in a straight tubular configuration. The use of such stents to treat diseased vessels at or near a bifurcation (branch point) of a vessel may create a risk of compromising the degree of patency of the main vessel and/or its branches, or the bifurcation point and also limits the ability to insert a branch stent into the side branch if the result of treatment of the main, or main, vessel is suboptimal. Suboptimal results may occur as a result of several mechanisms, such as displacing diseased tissue, plaque shifting, vessel spasm, dissection with or without intimal flaps, thrombosis, and embolism.
As described in related copending U.S. patent application Ser. No. 08/744,022 filed Nov. 4, 1996, now abandoned, Ser. No. 09/007,265 filed Jan. 14, 1998, Ser. No. 08/935,383 filed Sep. 23, 1997, U.S. Provisional Application No. 60/088,301 filed Jun. 5, 1998, and PCT Patent Application Publication No. WO 99/00835 filed Jan. 14, 1998, systems have been developed for deploying a main stent in a main vessel at the intersection of a main vessel and a branch vessel with a branch stent extending into a branch vessel through a side opening in the main stent. Unfortunately, several difficulties exist when attempting to position such an arrangement of a main and branch stents at a vessel intersection.
For example, the insertion of separate guidewires into both the main vessel and the secondary vessel is required before positioning a main stent in a main vessel with a branch stent projecting through a side opening in the main stent into a branch vessel. Main and branch stents are then advanced over the separate guidewires which have been pre-guided one after another into the respective main and branch vessels, such that the main stent can be deployed within the main vessel and the branch stent can be deployed through the side opening in the main stent into the branch vessel. Unfortunately, when attempting to guide two such separate guidewires through the main vessel such that one enters the branch vessel, the two guidewires typically tend to wrap around one another and become entangled. Additionally, time and effort is required to individually position each of the two guidewires one after another.
An additional disadvantage of conventional stents is the difficulty in visualizing the stents during and after deployment, and in general, the fact that they are not readily imaged by low-cost and easy methods, such as x-ray or ultrasound imaging.